QMYSQL , QPSQL , QPSQL7 ! Driver not found

tmapp · 23 Sept 2020, 15:32

Hi,
I'm new at using QT with database ; i've been developing using many dev language and this time i wanted to learn QT & C++ in order to start creating embedded soft.
When i try to load QMYSQL or QPSQL or QPSQL7 does not work.
My QT Version is 5.15 ; OS: Windows 10 64
and i tried the solutions provided on the documentation but does not work !!! My App need to be x32 so i'm using Mingw32 and the tool is MinGw81_32 . Any Help Please !?

JonB · 23 Sept 2020, 15:45

@tmapp said in QMYSQL , QPSQL , QPSQL7 ! Driver not found:

When i try to load QMYSQL or QPSQL or QPSQL7 does not work.

You should copy & paste the error message you receive when you have such a problem.

In any case, the answer is always the same for this issue: you need to set environment variable named QT_DEBUG_PLUGINS to value 1. If running your program from Command Prompt:

set QT_DEBUG_PLUGINS=1
/path/to/your/application.exe

Or if you run your app from Qt Creator it has a "Run Environment" or similar where you can set this variable.

Your program will then produce lines of diagnostic output indicating where your problem emanates from.

tmapp · 23 Sept 2020, 15:54

@JonB
The Error Message Always say : QSqlDatabase: QPSQL driver not loaded
QSqlDatabase: available drivers: QSQLITE QODBC QODBC3 QPSQL QPSQL7
in the moment where : qpsql*.dll exists in sqldrivers folder. I even tried the exemple found in the projects about the SQL database, in the selection there is PSQLITE, QPSQL and QODBC , but when using QPSQL and i give the information about the connection same Error : driver not loaded

JonB · 23 Sept 2020, 16:09

@tmapp
I told you exactly what & why you need to do with the environment variable. Did you act on that?

tmapp · 23 Sept 2020, 16:14

@JonB
Yep I did :
------------------------------------ Information -------------
section .gnu_debuglink not found in C:\Qt\QT5\5.15.1\mingw81_32\plugins\sqldrivers\qsqlpsql.dll.debug
section .gnu_debuglink not found in C:\Qt\QT5\5.15.1\mingw81_32\plugins\sqldrivers\qsqlpsql.dll.debug
QSqlDatabase: QPSQL driver not loaded
QSqlDatabase: available drivers: QSQLITE QODBC QODBC3 QPSQL QPSQL7
QSqlDatabase: QPSQL driver not loaded
QSqlDatabase: available drivers: QSQLITE QODBC QODBC3 QPSQL QPSQL7

AND on the QT SQL Browser : an error occured while opening the connection : Driver not loaded Driver not loaded.

JonB · 23 Sept 2020, 16:22

@tmapp
That is not the output I would expect with QT_DEBUG_PLUGINS=1. I would expect more detail. Can you show me how you set that, as this would not be the first time someone has not succeeded in doing so successfully.

tmapp · 23 Sept 2020, 16:24

@JonB
in the project setting i added it in the environement build :

and the last output i'm getting now :
Cannot load library C:\Qt\QT5\5.15.1\mingw81_32\plugins\sqldrivers\qsqlpsql.dll: The specified module could not be found.
QLibraryPrivate::loadPlugin failed on "C:/Qt/QT5/5.15.1/mingw81_32/plugins/sqldrivers/qsqlpsql.dll" : "Cannot load library C:\Qt\QT5\5.15.1\mingw81_32\plugins\sqldrivers\qsqlpsql.dll: The specified module could not be found."
QSqlDatabase: QPSQL driver not loaded
QSqlDatabase: available drivers: QSQLITE QODBC QODBC3 QPSQL QPSQL7

Christian Ehrlicher · wrote on 23 Sept 2020, 16:24

As always with this topic (the forum search function is a nice tool btw...) make sure the required libraries for the plugin are in the PATH.

JonB · T tmapp 23 Sept 2020, 16:22

@tmapp
So you have only just done that change now? At least it tells us something then: is the qsqlpsql.dll file indeed not in the directory it shows you it is looking for it?

tmapp · 23 Sept 2020, 16:41

the specified file exist in the path :

JonB · 23 Sept 2020, 16:44

@tmapp
I am not an expert here, but: I believe that if that .DLL file has missing dependencies (other DLLs) which it cannot find or cannot load, the error message you get is that the first one "could not be found", like yours shows. There is some Windows Dependency Walker app you can download which would allow you to see what other DLLs that DLL needs.

That's all I know, unless someone else knows better. You might find other references if you Google/search this forum for QPSQL driver not loaded.

mchinand · 23 Sept 2020, 16:50

@JonB Yes, the Postgres client dll (libpq.dll) and its dependencies also need to be in your path. I'm not sure if the libpq.dll and its dependencies that come with Postgres are compatible with minwgw.

JonB · T tmapp 23 Sept 2020, 16:34

@tmapp
See @mchinand's post above, this is just the sort of cause. And I can leave you in his hands :)

tmapp · wrote on 23 Sept 2020, 16:50

@mchinand
i copied files in the bin path of the mingw folder (libpq.dll and other dll found in a video of postgresql in youtube ) but doesn't work. I started by Mysql and when i saw qpsql*.dll I changed to it but same errors.
@JonB first thank you very much for your help and time , second yeah naturally i google it before , this is my first time posting a question in a forum, all times i google, but this one !

mchinand · 23 Sept 2020, 19:50

libpq.dll is for connecting to a Postgresql database not a Mysql database (not sure why you mentioned MySql in your most recent reply). Also, these dlls will also have to be 32-bit since your application is 32-bit.

tmapp · wrote on 23 Sept 2020, 19:50

@mchinand the dlls are 32bit, and about Mysql , it's just mentioning that i tried MySQL first and yet the same problem goes for PostgreSQL dunna know why! only QSQLITE WORK !!!

mchinand · 23 Sept 2020, 22:59

Where did you get the libpq and related dlls? You should copy them to the same folder as your project's executable (looks like build-sqlbrowser-Desktop_Qt_15_1_MinGW_32_bit-Debug) or add whatever folder they are in to your PATH environment variable (and restart QtCreator aftewards).

tmapp · wrote on 23 Sept 2020, 22:59

@mchinand same problem , no result . I even tried to remake the driver yet an error occured when making :

g++: error: unrecognized command line option '-std=c++1z'
g++: error: unrecognized command line option '-Wshift-overflow=2'
g++: error: unrecognized command line option '-Wduplicated-cond'
mingw32-make[2]: *** [Makefile.Release:403: .obj/release/qsql_sqlite.o] Error 1
mingw32-make[2]: Leaving directory 'C:/Qt/QT5/5.15.1/Src/qtbase/src/plugins/sqldrivers/sqlite'
mingw32-make[1]: *** [Makefile:45: release] Error 2
mingw32-make[1]: Leaving directory 'C:/Qt/QT5/5.15.1/Src/qtbase/src/plugins/sqldrivers/sqlite'
mingw32-make: *** [Makefile:50: sub-sqlite-make_first] Error 2

tmapp · wrote on 24 Sept 2020, 00:33

Hi Again , I solved the problem :: i had to remake the driver and after googling and looking in the forum many guys had the same problem with the actual driver and remaking new one. Here is how to do :

I'm using Postgresql 10.

1. you need to download the zip file of postgresql where source code exist.
2. lunch the Qt Mingw console.
3. copy all the file exists in the include path of the download zip in %Path_TO_QT\src\qtbase\plugins\sqldrivers\psql  
  ( if you don't you'll have problems with include files .h in mingw32-make
4. make sur to copy the lib files to the same folder psql ( libpq.dll , libeay32.dll, libintl , libiconv, ssleay32.dll ) ssleay32 you can have i from the net ( i got it from my xampp folder) 
5. edit the file psql.pro and comment : QMAKE_USE += psql  with a #
  if you don't you'll have error : psql model not defined
6. run the qmake command as follow: qmake "INCLUDEPATH+=PATH_TO_DOWNLOAD_SOURCE\pgsql\include" "LIBS+=PATH_TO_DOWNLOADED_SOURCE\pgsql\lib" psql.pro
  here PATH_TO_DOWNLOAD_SOURCE mean the path to the download zip extracted
7. run mingw32-make
8. run mingw32-make install

Congrats.
@Christian-Ehrlicher @JonB @mchinand thanks for your time and help :)